Any and all opinions or ideas are appreciated. I do have some questions though;

1) By choosing Windows XP x64 Edition, will I have compatability issues with my hard drives or other componants?2) The total price for this build is around 800GBP / $1500-ish; how is this price for the things I am getting?

As mentioned above, any help will be gladly recieved, thank you for your time.

You have a SLI motherboard, but are using an ATI graphic card. Although it would work fine as a single card GPU, you wouldn't be able to add another card for SLI. If you want to use just a single graphic card then you could save money by going with a P35 or a newer P43/P45 motherboard. If you want to go with a crossfire set up then go with a X38/X48 motherboard.about the same price for an Intel X48 Gigabyte motherboardhttp://www.ebuyer.com/product/145368/show_product_specifications?spectype=extendedabout the same price point, better Intel CPU E8200 http://www.ebuyer.com/product/139967I would stick with the XP 32 bit or if you want 64 bit then go with Vista